The ocean ecosystems are in trouble and losing species fast, which could leave no seafoodto harvest before 2050 if the current global trend continues, said researchers Thursday.

"This loss of species is threatening the sustainability of not only fishing, but … also other human uses of the ocean," said Boris Worm of Dalhousie University, lead author of the study published in the journal Science.

"This trend is negative for human well-being, meaning it has direct impacts on our economies and livelihoods."

The loss of biodiversity is reducing the ocean's ability to produce seafood, resist diseases, filter pollutants, and rebound from stresses such as over-fishing and climate change.

The research suggests that every species lost increases the decline of the overall ecosystem. On the other hand, every species recovered adds to the total productivity and stability of the ecosystem and its ability to withstand stresses.

Based on their findings,researchers project there will be no seafood species leftto consume before 2050— but they say it's not too late to change.

"We can see the bottom of the barrel, but it's not too late to turn it around. We're very optimistic about the recovery potential of the ocean ecosystem at this point in time," said Worm.

The authors say that restoring marine biodiversity through ecosystem-based management is essential in avoiding "serious threats to global food security, coastal water quality and ecosystem stability." They suggest integrated fisheries management, pollution control, maintenance of essential habitats and creation of marine reservestoaid in the recovery.

"We have to be selective about what we dump into the ocean and how it affects those ecosystems. We need to be smart about protecting sensitive regions," said Dr. Worm.

The four-year analysis is the first to look at all existing data on ocean species and ecosystems, in an effort to understand the importance of biodiversityon the global scale.

Researchers examined 32 controlled experiments, observational studies from 48 marine protected areas, and global catch data from the UN's Food and Agriculture Organization's database of all fish and invertebrates worldwide from 1950 to 2003.

The scientists also looked at thousand-year time series for 12 coastal regions, drawing on data from archives, fishery records, sediment cores and archeological data.

The study was funded by the National Science Foundation, the University of California and UC Santa Barbara.